| ASA is a kind of polymer with double layer or multi-layer Core-shell structure,which core is acrylate rubber and the shell is polystyrene and acrylonitrile. The typesof ASA with the shell or the core cross-linking, the molecular chains through eachother called LIPN.The core/shell ASA resin become the best modifier of PVC always used inoutdoor and has aroused wide concern, because with an excellent tougheness, heatdeformation-resistant properties, a wider processing temperature range and goodweatherability. However, due to the existence of technical barriers, the developmentof ASA impact modifiers in China is relatively slow, it has no industrialization now.In this paper, the work was focused on the two difficulties in the preparationtechnology of ASA resin, there are, how to improve the strength between the twophase of ASA and the compatibility between ASA and the matrix of PVC. In order tosolve this problem, three kinds of high performance ASA latex were synthesized bypre-emulsion multi-step seeded emulsion polymerization, which can realize theeffective controlling of the particle size and cross-linking density, analyzed themechanism of cross-linking density，the modification for PVC was studied. Thetoughening mechanism was researched, and the effect of synthetic parameters on themodification were discussed. The main research work are as follows:1. According to the polymerization conditions which was selected, wesynthesized three kinds of ASA by step seeded emulsion polymerization, threedifferent ways were taken to combining two phase together and to improve theadhesion between them, according to the ways of that, called them as simplecore-shell type, the transitional type and the cross-linking type (LIPN); realized theparticle size controllable by exploring the relationship between the dosage of the seedand latex particle size of the PBA; studied difference between them through TEM, SEM, DSC and mechanical test, and found that LIPN-Ⅰwhich was cross-linked byMAA has optimal performance.2．On the basis of LIPN-Ⅰ, introduced shell monomer and cross-linking agentinto the core, and synthesized LIPN-Ⅱwith a controllable cross-linking density,which has copolymer in the core. And then tried to modified LIPN-Ⅱby silanecoupling agent.3．The control of cross-linking density was based on cooperate of the emulsifierSDS, AES and MAA, studied the mechanism of that MAA cross-linking by FT-IR、DSC methods.4．The preparation and properties of PVC/ASA blends were investigated. Highperformance PVC/ASA blends were prepared by mixing ASA copolymer with PVC.And the LIPN-Ⅲ modified PVC has the best impact strengh.The research on mechanism of ASA toughening PVC was carried by using SEMstudied the dispersion of ASA in PVC matrix, and further researched the tougheningmechanism, the results show that the plastic phase in the core of LIPN-Ⅱcan promoteits dispersion in PVC.Investigation the factors of ASA it self on the influence of modified, it was foundthat the particle size of PBA and its contents had less influence on the tensile strength,while it had great influence on the impact strength of PVC/ASA blends. There existsan optimum particle size range to obtain high performance alloy. The PVC/LIPN-Ⅰcan reach the maximum impact strength55.6KJ/m2when the rubber particle size wasabout200nm and the content of BA was about65%; And we also found that in therange of1.5%~2.7%, the increase of MAA dosage in Synthesis will promote blendsimpact performance improvement.For LIPN-Ⅱ, there exist optimum values of the core-shell ratio, rubber andplastic ratio and cross-linking density to obtain the optimum mechanical property.When the BA content was in the range of40~50%, dosage of cross-linking agentwas about1.5%, gel. content was in88~90%, PVC/LIPN-Ⅱblends can be reach themaximum impact strength.The modification for LIPN-Ⅱby silane coupling agent had little influence on theimpact strength of PVC/LIPN, but some degree of improvement in heatdeformation-resistant and processing can be observed. |
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